When you create an account, your default privacy setting is Friends and Club Only. This means that only your Track Rabbit friends and fellow club members will see your event attendance and vice versa.
That said, once you've added friends or verified your club membership, you can view other friends and members' event attendance by heading to the event details of an event or heading to an individual's user profile.
If you're not a member of a club or have any Track Rabbit friends yet, you can still see all of the vehicles that are attending an event and which run group they're in by clicking Vehicles under Who's Going on an event details page.
To learn more about privacy settings, please check out this article